No, its not possible at the moment. But theoretically it could be done: We have blur, we have edge detection - and both together could be used to denoise. The edge detection would determine where the blur should not take place. (Areas with contrast).
To denoise certain noise patterns you really need special software. Not sure if Cockos would make such an effort as this can usually be found in software with main focus on graphics.
But it seems we need a thread for collecting ideas and features about video in Reaper. Though I'm pretty sure this would explode all expectations.
